There are various existing methods to manufacture metal-oxide-semiconductor (MOS) devices. For example, as shown in FIG. 1, a current method to form a MOS device includes: providing a semiconductor substrate 100; covering the surface of the semiconductor substrate 100 with an insulation layer 101; covering the surface of the insulation layer with a polycrystalline silicon layer 103; covering the surface of the polycrystalline silicon layer 103 with a photoresist layer 105.
Further, as shown in FIG. 2, the current method includes: etching the polycrystalline silicon layer 103 and the insulation layer 101 using the photoresist layer 105 as a mask to expose the substrate 100; forming a polycrystalline silicon layer 103a and an insulation layer 101a, wherein the polycrystalline silicon layer 103a is on the surface of the insulation layer 101a; 
As shown in FIG. 3, the current method further includes: after forming the insulation layer 101a and the polycrystalline silicon layer 103a, doping ions are implanted into the semiconductor substrate 100 using the photoresist layer 105 as a mask to form source/drain regions 107.
However, with the development of the semiconductor process technology, the process node decreases gradually, and the gate critical dimensions (CD) also continuously decreases, which may cause the MOS devices manufactured by the current methods to have stability issues. The disclosed methods and systems are directed to solve one or more problems set forth above and other problems.